The present invention relates to a disk cartridge, such as an optical disk cartridge or a magnetic disk cartridge and the like, and more particularly to the structure of a disk cartridge in which a large type head may be used.
In recent years, along with the accelerating development of multimedia, optical information recording drives capable of recording a large quantity of data in high density and reproducing them at high speed are attracting a great deal of attention. These optical information recording drives include a read-only type optical disk, such as a CD or a laser disk, on which information is stamped on the disk at the time of producing the disk which thereafter permits only reproduction of the recorded information, a write-once type optical disk, such as a CD-R, which permits only once recording, and a rewritable type optical disk which permits rewriting and erasing of data without limitation by utilizing photomagnetic recording or phase change recording. Of these available types of optical information recording drives, optomagnetic recording drives are mainly used in the field where a high data transfer rate is required.
Recording and reproduction of data use a light spot obtained by narrowing down a laser beam to the diffraction limit of the lens. The size of this light spot is almost equal to xcex/NA, where xcex is the wavelength of the laser beam and NA, the numerical aperture of the lens. Recording and reproduction in higher density, i.e. of a smaller pattern, requires a correspondingly smaller light spot.
In order to reduce the size of the light spot, the numerical expression of xcex/NA teaches two manners: one decreasing the wavelength xcex of the laser beam, and the other of increasing the numerical aperture NA of the lens. The lens numerical aperture NA, represented by NA =sin xcex8 where xcex8 is the half diaphragm angle, is smaller than 1.
In any optical information recording drive currently in practical use, the numerical aperture NA of the objective lens is at most about 0.6. This is because, as the numerical aperture NA increases, the coma and the astigmatism aberrations become greater in a state wherein the optical axis of the objective lens is inclined with respect to the substrate.
In order to solve this problem, it is essential not only to reduce the thickness of the transparent layer which the light passes (corresponding to the thickness of the transparent substrate in conventional optical information recording drives) but also to prevent the optical axis of the objective lens from being inclined with respect to the transparent substrate. For this purpose, there is proposed an optical information recording medium, together with a manufacturing method thereof, having grooves and pits for obtaining signals at the time of tracking and address signals formed on the transparent substrate, a recording layer including a reflective layer formed over them and a transparent resin layer of about 0.1 mm in thickness further formed over it. Recording and reproduction of information are accomplished by pressing a slider which mounts an objective lens and the like, against the surface of the transparent resin layer of this information recording medium (see JP-A-8-235638).
This optical information recording medium, however, there arises a problem that, because the slider is moved while being pressed against the transparent resin layer, the friction between the slider and the transparent resin layer is apt to result in scratching the transparent resin layer.
Moreover, the transparent resin layer over the recording layer is formed by either spin-coating it with ultraviolet setting resin or adhering a transparent resin film to it. Where a transparent resin film is to be adhered, it has to be ensured that no air pockets or bubbles are formed between the film and the recording layer, but this requirement poses a productivity problem.
Furthermore, where the ultraviolet setting resin coat is to be formed in a thickness of about 0.1 mm, the viscosity of the resin should be set considerably higher than usual, because this thickness is about five to ten times as great as the 10 to 20 xcexcm thickness of a usual protective layer for an optical information recording medium. In this case, there are problems about the uniformity of the transparent resin layer and of possible generation of bubbles from air rolled in, which entail productivity and yield implications as in the case of adhering a transparent resin film.
On the other hand, a near field optical recording/reproducing system is proposed, by which light is focused on an information recording medium via a solid hemispherical lens (SIL), the distance between the SIL and the surface of the optical information recording medium is set to be about xc2xc xcex (xcex is the wavelength of the laser beam), and the NA of the objective lens is effectively enhanced by using near field light (see U.S. Pat. No. 5,125,750).
However, in this system again, where the wavelength of the laser beam is 650 nm, the distance between the bottom surface of the SIL and the surface of the optical information recording medium is as little as 160 nm, which implies the problem of possible scratching of the surface of the optical information recording medium by the SIL. As a consequence, the cartridge to accommodate the disk has to be designed to minimize sticking of dust to the disk surface when the disk is not in use.
On the other hand, these recording systems allow recording onto and reproduction from both sides of the disk. However, this entails doubling of the height and size of the head, which is particularly unavoidable in the optical assist magnetic recording/reproducing technology, which is expected to make possible even higher density for information recording media.
This optical assist magnetic recording/reproducing technology is intended to achieve both high line recording density, an advantage of vertical magnetic recording, and high track density, a feature of optical recording by irradiation with a laser beam in an assisting way at the time of vertical recording/reproduction (see the Journal of the Magnetics Society of Japan, Vol. 23, No. 8, 1999).
This problem has led to a requirement for a disk cartridge having a large head inlet, but a conventional disk cartridge has a rectangular head inlet formed as a block in a prescribed position of a cartridge case. Where an enlarged head is to be used on account of the above-described background circumstance, the surrounding portions of the case demarcating the head inlet would pose obstacles, which a disk cartridge loaded into the recording/reproducing apparatus might collide against and thereby give rise to various troubles.
FIGS. 19 and 20 are drawings illustrative of a disk cartridge proposed in the Japanese Utility Model Laid-Open No. 4-26463 specification. This disk cartridge is provided with an upper case 100a and a lower case (not shown) constituting a cartridge case 100 and to be separable from each other in the vertical direction. In respectively prescribed positions of the cartridge case 100, there are formed a head insertion inlet 101 and a spindle insertion inlet 105, and a recording disk 102 is accommodated rotatably within the cartridge case 100.
A shutter 103 for opening and closing the head insertion inlet 101 is arranged slidably on the cartridge case 100. When a disk cartridge is inserted into a disk drive unit, the shutter 103 shifts in a direction orthogonal to the direction of disk cartridge insertion, and the head insertion inlet 101 and the spindle insertion inlet 105 are opened. To the front and rear ends of the shutter 103 is connected a slider 104 to make the shutter 103 more slidable. The upper case 100a and the lower case are elastically energized by a spring member (not shown) in the direction of joining each other, and at the same time they are separated in the vertical direction by the shifting of the slider 104.
This disk cartridge involves an inconvenience that, where a larger head is to be used, the surrounding portions of the case demarcating the head insertion inlet 101 would pose obstacles, and the head might collide against those case portions. One of the reasons of impossibility to widen the head insertion inlet 101 is related to the shutter 103.
That is, while the shutter 103 shifts in a direction orthogonal to the direction of disk cartridge insertion to open or close the head insertion inlet 101, the head insertion inlet 101 is formed in the central part of the cartridge case 100 as its location is conditioned by its positional relationship with the head, and full closing of the head insertion inlet 101 requires a slightly greater width of the shutter 103 than that of the head insertion inlet 101. On the other hand, full opening of the head insertion inlet 101 requires a space for use in standing by wider than the shutter 103 beside the head insertion inlet 101 to let the shutter to shut. At the same time, the width of the cartridge case 100 is determined by its relationship with the disk drive unit, and the above-noted requirements eventually limit the width of the head insertion inlet 101 and make it difficult to use a large enough head.
The object of the present invention is intended to remove such defects of the prior art and provide a disk cartridge made adaptable to an enlarged head as well by letting a large portion of the recording disk be exposed out of the cartridge case.
In order to attain the above-noted object, first means according to the present invention is a disk cartridge provided with a recording disk and a cartridge case for accommodating that recording disk, in which: the cartridge case is divided on its plane into at least a first case portion and a second case portion, and the second case portion is arranged slidably relative to the first case portion; the recording disk is enabled to be covered by the first case portion and the second case portion by keeping the first case portion and the second case portion in a parallel state when the disk cartridge is not in use; and, when the disk cartridge is in use, a disk freeing portion wherein parts of both inside face and outside face of the recording disk are exposed from the cartridge case by moving the second case portion relative to the first case portion.
Second means according to the present invention is a version of the first means in which the second case portion shifts in the direction reverse to the direction of disk cartridge insertion into a disk drive unit.
Third means according to the present invention is a version of the second means in which the ratio of the width L1 of the disk freeing portion in the direction orthogonal to the shifting direction of the second case portion to the width L2 of the disk cartridge in the direction orthogonal to the shifting direction of the second case portion (L1/L2) surpasses 0.5.
Fourth means according to the present invention is a version of the first means in which guide members protrude in parallel with each other in the same direction from both sides of the first case portion, the second case portion are supported by the guide members and, by shifting the second case portion relative to the first case portion, the disk freeing portion is formed inside the guide members.
Fifth means according to the present invention is a disk cartridge provided with a recording disk and a cartridge case for accommodating that recording disk, in which: a disk freeing portion wherein parts of both inside face and outside face of the recording disk are exposed is formed toward the tip of the cartridge case, a shutter for opening and closing the disk freeing portion is fitted shiftably to the cartridge case so as to shift in the direction reverse to the direction of disk cartridge insertion into the disk drive unit, and the ratio of the width L3 of the disk freeing portion in the direction orthogonal to the shifting direction of the shutter to the width L4 of the disk cartridge in the direction orthogonal to the shifting direction of the shutter (L3/L4) surpasses 0.5.
Sixth means according to the present invention is a version of the fifth means in which the size of the shutter does not permit it to project from the rear end of the cartridge case when the disk freeing portion is opened.
Seventh means according to the present invention is a version of the sixth means in which a stopper section for regulating the opening position of the shutter is provided at the rear end of the cartridge case.
Eighth means according to the present invention is a version of the sixth means in which a spindle insertion inlet is formed in the cartridge case, a hub is fitted in the central part of the recording disk and, when the disk cartridge is not in use, the hub blocks the spindle insertion inlet.
Ninth means according to the present invention is a version of the fifth means in which an end blocking piece for covering sides of the disk freeing portion is provided at the tip of the shutter, and the end blocking piece is elastically energized in the direction of covering the sides of the disk freeing portion.
Tenth means according to the present invention is a version of the fifth means in which a linking portion having substantially the same thickness as the recording disk is provided integrally toward the tip of the cartridge case so as to stride over the disk freeing portion.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.